The present invention relates generally to surgical probe for use in liquid media, and in particular to pulsed electro-surgical and laser probe for preventing formation of liquid jet in liquid media.
Fiber-delivered laser pulses and pulsed electrical discharges are applied in surgical procedures for precise dissection of soft tissue in liquid media. Energy deposition results from either absorption of the laser radiation in fluid or in tissue, or from localized electric discharge in front of the microelectrode. In liquid media, energy deposition leads to explosive evaporation of fluid and is accompanied by formation of a vapor bubble that can cause substantial collateral damage during its growth and, especially, during the collapse. In fact, collapsing vapor bubbles are the main source of collateral damage in intraocular surgical applications of focused or fiber-delivered pulsed lasers and pulsed electric discharges. When the vapor bubble formed on a tip of an optical fiber probe or on an electric probe collapses, it usually produces a liquid jet in the direction of the probe. This flow of liquid propagates along the axis of the probe and produces tissue damage far beyond the primary energy deposition zone. Repetitive application of laser pulses can also result in formation of a steady flow that pushes soft tissue in front of the probe and interferes with surgery.
xe2x80x9cElectrical Alternative to Pulsed fiber delivered Lasers in Microsurgeryxe2x80x9d, Journal of Applied Physics 81(11): 7673-7680 (1997) by Daniel Palanker et al. discloses a method for intracular microsurgery based on cavitation bubble generation by electric discharge. In this approach, the expanding cavitation bubble is used to provide cutting action. A limitation of using the cavitation bubble for cutting is that only very soft tissue (e.g. retinal tissue) can be cut. Relatively hard tissues such as eye lenses, lens capsules (e.g. in a capsulotomy procedure) or irises can not be cut by the method disclosed by Palanker. Yet another disadvantage of the method of Palanker is that cavitation bubbles produce substantial collateral damage to surrounding tissue due to generation of liquid flow during bubble collapse.
U.S. Pat. No. 6,135,998 issued to Daniel Palanker discloses a technique for dissection of tissue by short electric discharge in conducting fluids that create plasma streamers and result in explosive evaporation of water in the vicinity of the probe. Collateral tissue damage in this technique is also associated with collapsing cavitation bubbles.
U.S. Pat. Nos. 6,066,134, 5,891,095, 5,697,536 and 5,697,281 disclose a tip of an electro-surgical probe, wherein the tip has a generally cylindrical body portion, e.g. a portion of a shaft, and a substantially xe2x80x9cthin and flatxe2x80x9d distal end surface. These prior art references teach that the distal end surface of the tip can be planar, concave, convex, hemispherical, conical and so on in order to facilitate access to certain body structures in electro-surgical procedures. In these prior art references, the body portion of the tip is generally a cylindrical shaft or a blunt shaft (a portion of a convex cone). The geometry of the body portion of the tip (especially the portion just after the distal end surface of the tip) does not play a role in their teachings regarding reducing tissue damage caused by the liquid jet resulting from the collapse of the cavitation bubble.
U.S. Pat. No. 5,658,279 discloses a bipolar electro-surgical tissue penetrating probe having a tip which comprises a conical body portion, or a pyramid body portion, or a blunt body portion, or an annulus body portion. This prior art reference does not discuss situations related to applications of the probe in liquid media. The geometry of the body portion of the tip (especially the portion just after the distal end surface of the tip) also does not play a role in this teaching regarding reducing tissue damage.
In view of the above, it would be an advance in the art to provide a surgical probe for use in liquid media having a novel tip geometry which can substantially reduce or completely eliminate the liquid jet resulting from the collapse of the cavitation bubble so as to substantially lower the tissue damage.
In view of the above, it is a primary object of the present invention to provide a surgical probe for use in liquid media having a tip, wherein the tip has a concave body portion and a distal portion, such that the liquid jet resulting from the collapse of the cavitation bubble can be substantially reduced and relevant tissue damage can be substantially lowered or even eliminated.
It is an another object of the present invention to provide a surgical probe having a tip with a concave body portion comprising two or more stages stacked together substantially along the longitudinal direction of the probe.
It is a further object of the present invention to provide a surgical probe for use in liquid media having a tip and an obstacle, wherein the tip has a body portion and a distal portion, such that the liquid jet resulting from the collapse of the cavitation bubble can be substantially reduced or even eliminated and relevant tissue damage can be substantially lowered. The obstacle can be a ring positioned on or after the body portion or a pick positioned on one side of the probe and/or in front of the probe.
These and numerous other objects and advantages of the present invention will become apparent upon reading the detailed description.
The present invention provides a surgical probe having a tip for use in liquid media, wherein the tip has a concave body portion and a distal portion. The concave body portion of the tip is positioned after the distal portion such that the liquid jet resulting from the collapse of the cavitation bubble can be substantially reduced, or even eliminated.
The present invention also provides a surgical probe having a tip and an obstacle for use in liquid media, wherein the tip has a body portion and a distal portion. The obstacle, e.g. a ring, is positioned on the outside of the probe such that the liquid jet resulting from the collapse of the cavitation bubble can be substantially reduced. The obstacle can also be a pick positioned on one side of the probe and/or in front of the probe.
In accordance with the present invention, by changing the geometrical shape of the tip, the liquid flow caused by collapsing bubbles can be substantially reduced and even inverted. During collapse of the bubble, the liquid flow on the back side of the probe with a convex body portion accelerates more than that on the front since the probe occupies increasingly larger part of the area of the liquid/gas boundary. Thus, such a flow will be decelerated on the outer surface of the concave body portion of the tip of the present invention, where the probe occupies increasingly smaller part of the liquid/gas boundary as the bubble collapses.
The concave body portion of the probe according to the present invention is a portion which has at least a portion of a concave cone with circular generatrix, or at least a portion of a concave cone with elliptic generatrix, or at least a portion of a concave cone portion with parabolic generatrix, or at least a portion of a concave cone with hyperbolic generatrix, or their combinations, or any other regular or irregular concave shapes. The concave body portion can also have two or more stages stacked together substantially along the longitudinal direction of the probe. For example, the concave body portion can have two or more stages (with linear generatrix) selected from the group consisting essentially of cylindrical stage, conical stage and planar stage.
The concave body portion of the tip is generally symmetrical with respect to the longitudinal axis of the probe. However, the concave body portion can also be asymmetrical with respect to the longitudinal axis of the probe.
The dimension of the concave body portion of the tip can be similar to or substantially larger than those of the distal portion of the tip along a longitudinal direction of the tip and the maximal radius of the concave body portion along a horizontal direction of the tip can be similar to or substantially larger than that of the distal portion of the tip.
The distal portion of the tip can be substantially flat, concave, partially concave, convex or partially convex. The distal portion can also have a shape selected from the group consisting essentially of plane, partial-sphere, hemisphere, pyramid, cone and cylinder. Generally, the distal portion of the tip is symmetrical with respect to the longitudinal axis of the probe. However, the distal portion can also be asymmetrical with respect to the longitudinal axis of the probe.
Similar effect of deceleration can be achieved using an obstacle, e.g. a ring, position behind the distal portion of the tip. This ring slows down the flow from the back of the tip thus reducing, eliminating or even inverting the liquid jet in front of the probe.
Formation of the forward-propagating liquid jet can also be prevented by placing an obstacle, e.g. a pick, on one side of and/or in front of the tip. Cavitation bubble is attracted to such an obstacle and collapses on it without forming the forward propagating liquid jet flow.
When working with a probe having an obstacle, the body portion of the tip can have at least a cylindrical portion, or at least a conical portion, or at least a concave portion, or at least a convex portion, or their combinations, or any other regular or irregular body shapes. The body portion of the tip is generally symmetrical with respect to the longitudinal axis of the probe. However, the body portion can also be asymmetrical with respect to longitudinal axis of the probe. The distal portion of the tip can be substantially flat, concave, partially concave, convex or partially convex. The distal portion can have any shape selected from the group consisting essentially of plane, partial-sphere, hemisphere, pyramid, cone and cylinder. Generally, the distal portion of the tip is symmetrical with respect to the longitudinal axis of the probe. However, the distal portion can also be asymmetrical with respect to longitudinal axis of the probe.
In accordance with the present invention, the probe of the present invention can be an electric probe, an optical wave-guide probe, any form of their combinations, or any other possible surgical probe for use in liquid media.
The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The figures and the detailed description more particularly exemplify these embodiments.